Apparatus for electric contact spot welding, preferably of small-size parts

ABSTRACT

The present invention relates to apparatus for electric contact welding, preferably, of small-size parts, wherein a movable rod supporting the top electrode holder is connected through at least one leaf spring to a mechanism adapted to develop a contact welding pressure. The end of this leaf spring is rigidly secured to the mechanism adapted to develop the contact welding pressure and the other end of this leaf spring freely bears upon the rod supporting the top electrode holder. The high-current electric conduit which supplies the welding current to the top electrode holder has a portion, adjacent to the top electrode holder, which extends perpendicularly to the housing of the bottom electrode holder.

[ 1 June 20, 1972 United States Patent Moravsky et al.

219/86 ....219/86 3,117,216 1/1964Stewart..............................,.....219/86 [541 APPARATUS FORELECTRIC 2,750,484 6/1956 CONTACT SPOT WELDING, 2,958,757 11/1960 Stolzet al..

PREFERABLY OF SMALL-SIZE PARTS [72] Inventors:

t c a t n o c .w r t c k e n r e :0 S M m m 2W m m Yw m A m a b w R o u.h T l mD S h B m A 1 Fuvm W IM m 1 8% m mwm v m a .m mmw m w 3. m mum Pl mmw 7 e TS! 5 h PAA T Vladislav Eduardovich Moravsky, Bulvar LesiUkrainki, 2, kv. 50; David Solomonovich Vorona, ulitsa Scherbakova, 51,kv. 21, both of Kiev; Boris Pavlovich Shinkarenko, ulitsa Sovetskaya, I,Fastov Kievskoi Oblasti, all of USSR.

Oct. 7, 1969 welding, preferably, of small-size parts, wherein a movablerod [22] Filed:

supporting the top electrode holder is connected through at [21 1 Appl'864,972 least one leaf spring to a mechanism adapted to develop acontact welding pressure. The end of this leaf spring is rigidly securedto the mechanism adapted to develop the contact welding pressure and theother end of this leaf spring freely bears upon the rod supporting thetop electrode holder. The high-current electric conduit which suppliesthe welding cur- 606 BN w k7 33% 8 LA 9m 1 [51] Int. [58] Field of rentto the top electrode holder has a portion, adjacent to the ReferencesCited top electrode holder, which extends perpendicularly to the housingof the bottom electrode holder.

UNITED STATES PATENTS 2,727,122Gartner...................................219/86 2Claims,3DrawingFigures 2 Sheets-Sheet 1 Patented June 20, 1912 Patented June 20,19723,671,708

2 Sheets-Sheet 2 V Fi .5 3 Q APPARATUS FOR ELECTRIC CONTACT SPOTWELDING, PREFERABLY OF SMALL-SIZE PARTS The present invention relates toelectric welding machinery, and, more specifically, it relates toapparatus for electric contact spot welding, preferably, of small-sizeparts employed in electronic devices, precision instruments,communication installations, and so forth.

Known in the art are apparatus for electric contact spot welding,particularly, of small-size parts, comprising a top electrode holder anda bottom electrode holder, disposed in the housing of the apparatus andconnected to a source of the welding current through respective electriccurrent conduits, e.g. bus wires. The top electrode holder isoperatively connected through a plurality of leaf springs with amechanism adapted to develop a welding contact pressure (see, forexample, Electrical Equipment for Precision Spot Welding by N.M.Sokolov,Privolzhskoye Publishing House, 1964).

Welding of small-size parts by this known apparatus is accompanied bysplashes of the molten metal out of the weld area, which molten metal isapt to solidify, eg on the constituent parts of an electronic orelectric vacuum device, thereby producing noise during operation of anelectronic or radio circuit employing such device. Moreover, it mightlead to reduced reliability of the performance of such circuits and totheir premature deterioration.

in this known apparatus, the movable rod of the top electrode holder isrigidly connected with leaf springs transmitting the welding pressurethereto, whereby during the welding operation, when the parts beingwelded are compressed between the electrodes, the alignment of the twoelectrodes can be affected, and the working surfaces of their adjacentends may become non-parallel. Consequently, a situation might occur inwhich the electric current and the welding pressure become non-uniformlydistributed over the contact area of the parts being welded, which bothaffects the quality of welding and leads to splashing-molten metalbeyond the weld area.

There are other types of known apparatus for electric contact spotwelding of parts (see, for example, US. Pat. No.3, 1 40,38 1 cl.21886and British Pat. No. 988,187, cl.B3A wherein the electrode holder isoperatively connected with a mechanism adapted to develop a contactwelding pressure through a pivot means and a system of levers. However,this causes the mass of the movable parts of the apparatus to beincreased, which results in poorer dynamic characteristics of theapparatus and, consequently, poorer quality of welding.

Additionally, in the known apparatus of the last-mentioned type, theelectric current conduit in the area thereof, adjacent to the topelectrode holder, extends substantially parallel to the current-carryinghousing of the bottom electrode holder. As a result, with the electricwelding current flowing through the above mentioned parts,electrodynamic forces are generated which tend to move the electrodesaway from each other, thus reducing the welding pressure, affecting thewelding operation and promoting conditions in which the molten metalmight be splashed out of the weld area.

There is still another known type of apparatus for electric contact spotwelding of small-size parts (see, for example, the specifications of thespot welding machine, Model SEC-60, marketed by the Minitubes Companywherein the top electrode holder is driven in operation through amechanism comprising springs and pivoted levers. In apparatus of thistype, in order to insure axial alignment of the working ends of theelectrodes and parallelism of their contact surfaces, the inclinationangle of the top electrode relative to a horizontal plane is adjustable.However, although at the moment when a desired welding contact pressureis developed, the working ends of the electrodes in this known apparatusare axially aligned, and their contact surfaces are parallel to eachother, in the course of the welding operation such alignment andparallelism might become affected, due to variations of the geometricalsize of the parts being handled and also to melting and crystallizationof the metal in the weld area.

There is another known type of electric contact spot welding apparatus(see the specifications of the machine, Model RChA, marketed by theOrigin Electric Co., Japan) in which the bottom electrode holder ismovable and springbiased in operation. However, in this known apparatus,the compression spring which is adapted to bias the bottom electrodeholder and upon which this holder bears in operation is alreadycompletely compressed at the moment the welding current is supplied tothe electrodes. Consequently, with this structure, the bottom electrodeis able to follow up any shrinking of the metal in the weld area, but isunable to follow up" the expansion of the metal.

It is an object of the present invention to provide an apparatus forelectric contact spot welding, particularly, of small-size parts,wherein the operative connection between the top electrode holder andthe mechanism adapted to develop a contact welding pressure providesaxial alignment of the working ends of the two electrodes andparallelism of the contact surfaces thereof during the stage ofcompressing the parts to be welded and also throughout the rest of thewelding operation.

It is another object of the present invention to provide an apparatusfor electric contact spot welding, wherein no unwanted electrodynamicforces affecting the contact welding pressure are developed.

It is another object of the present invention to provide an apparatus,wherein both electrodes are able to follow up the process of melting andcrystallization of the metal in the weld area.

With these and other objects in view, an apparatus for electric contactspot welding, preferably, of small-size parts, comprises, in accordancewith the invention a top electrode holder and a bottom electrode holderreceived in the housing of the apparatus and connected throughrespective electric current conduits to a source of the welding currentsupply, and a movable rod supporting this top electrode holder andoperatively connected through at least one leaf spring with a mechanismadapted to develop a welding pressure. In accordance with the presentinvention, the leaf spring has one extremity thereof rigidly secured tothe mechanism adapted to develop a welding pressure and the otherextremity thereof adapted to engage freely this movable rod supportingthe top electrode holder; the electric current conduit, which is adaptedto supply a welding current to the top electrode holder, having a partthereof disposed adjacent the top electrode holder, extending normallywith respect to the bottom electrode holder.

Owing to the above mentioned structural features, the apparatus forelectric contact spot welding, embodying the present invention, combinescomparatively low inertia of the movable parts with provisions forpositive axial alignment of the working ends of the two electrodes andfor parallelism of the contact surfaces thereof because, in thisapparatus, operating pressure is transmitted from the leaf springs tothe movable electrode holder without any rigid connection therebetween.Moreover, in the apparatus embodying the present invention, the actionof electrodynamic forces in the course of the welding operation ispractically eliminated since, in this apparatus, the electric currentsupply circuit does not coincide with the mechanical driving means, andthe electric current conduit which supplies the welding current to thetop electrode holder extends perpendicularly to the current-carryinghousing of the bottom electrode holder.

It is advantageous in the apparatus embodying the present invention, forthe bottom electrode holder to be mounted for vertical reciprocation inthe housing of the apparatus and to be adapted to engage freely oneextremity of at least one additional leaf spring, the other extremity ofthis additional leaf spring being rigidly secured to a stationary partof the housing of the apparatus. This structural feature provides forestablishing a faster closing motion of the electrodes during a weldingoperation, and it additionally enables the bottom electrode to follow upboth shrinking and expansion of the metal in the weld area. It alsoprovides for selecting various accelerations of the closing motion ofthe electrodes in the weld area independently of the value of a desiredwelding contact pressure.

The above-said features promote a higher quality of welding and minimizethe possibility of the molten metal being splashed out of the weld area.

The present invention will be better understood from the followingdetailed description of an embodiment thereof, with due reference beingmade to the accompanying drawings, wherein:

FIG. 1 is a longitudinal sectional view of an apparatus for electriccontact spot welding in accordance with the invention;

FIG. 2 is a cross-sectional view taken along line 11 II of FIG. 1; and

FIG. 3 is a longitudinal sectional view of a modification of the bottomelectrode holder assembly in an apparatus for electric contact spotwelding in accordance with the invention.

Referring now to the drawings, an apparatus for electric contact spotwelding, preferably, of small-size parts, comprises a housing composedof portions 1 and 2 (FIG. 1) supported on a base 3 made of anelectrically insulating material.

Disposed in the housing portion/are a top electrode holder assembly 4and a mechanism 5 for developing welding pressure, whereas a bottomelectrode holder assembly 6 is disposed in the housing portion 2.

The top electrode holder 4 is mounted on a rod 7 which is verticallyreciprocable in guides 8 of either a ball or a roller type.

Surrounding the upper end portion of the rod 7 is a coiled compressionspring 9, one end of the spring 9 bearing against a stationary surfaceof the housing portion 1 and the other end thereof permanently biasingthe rod 7 upwardly through a semi-spherical head 10 mounted on the upperend of the rod.

The mechanism 5 comprises a plurality of levers which are operativelyconnected with either a foot-actuated drive or a power drive (not shown)and a vertically reciprocable bar 11 movably mounted in roller guides 12supported by the housing portion 1.

Surrounding the lower portion of the vertically reciprocable bar 11 isanother coiled compression spring 13, one end of the spring 13 bearingagainst a radial shoulder of the bar 11 and the other end of the springbearing against the stationary base 3.

The guides 8, e.g. with spherical rollers 14 (FIG. 2) are so arranged inthe housing portion 1 that one of them can be slidably adjusted againstthe rod 7 and retained in an adjusted position by screws 15. Theadjustment is intended to prevent any oscillations, displacement oraxial rotation of the rod 7 in the course of its verticalreciprocations.

Screws 16 are provided for adjustably pressing the roller guides 12against a lateral side of the bar 11, in order to eliminate playtherebetween and thereby to prevent positively any displacement,rotation or oscillations of the bar 11 in the guides 12.

The upper end portion of the bar 11 (FIG. 1) has rigidly secured theretoone extremity of a stack of leaf springs 17 adapted to transmit awelding pressure. The other extremity of the stacked leaf springs 17freely bearing upon the head 10 of the rod 7. The end portion of the bar11 securing the springs carries a bracket 18 supporting a weldingpressure indicator 19.

The welding pressure is defined by the degree of the elastic deformationof the leaf springs 17 during the downward, working stroke of thereciprocable bar 1 l, and can be adjusted by means of a set screw 20which can be displaced in a vertical direction in relation to thebracket 18 by means of an adjustment nut 21. I

The set screw 20 has an axial bore therethrough slidably receiving astem 22, the bottom end of the stem 22 carrying a U-shaped piece 23adapted to operate a microswitch 24 connected in the control circuit ofthe welding current supply source (not shown) of the herein describedwelding apparatus,

whereas the upper end portion of the stem 22 projects above the adjacentend of the set screw 20.

In order to provide accelerated drawing of the welding electrodes, asthey are moved toward each other for a welding operation, and also toenable the bottom electrode to follow" shrinking and expansion of themetal in the weld area, the bottom electrode holder 6 (FIG. 3) may bemounted on a rod 25 which can be vertically reciprocated along guides26, e.g. of a ball or a roller type. In this modification, the bottomextremity of the rod 25 has attached thereto a semi-spherical head 27which bears freely upon the free end portion of a stack of cantileverleaf springs 28 whose other end is rigidly secured to the base 3 of theapparatus.

The electrodes 29 and 20 are releasably secured, respectively, in theelectrode holders 4 and 6 and the latter can be rotatively adjusted toany desired angular position about the axes of the rods 7 (FIG. 1) and25 (FIG. 3), respectively. The welding current supply source (not shown)is connected with the electrode holder 4 (FIG. 1) through a high-currentconduit 31 and with the electrode holder 6 through a high-currentconduit 32, the flexible portion of the conduit 31 extendingsubstantially perpendicularly to the portion 2 of the housing of theapparatus.

The herein described welding apparatus operates, as follows.

Electrodes 29 and 30 of a type suitable for the job to be performed aremounted and secured in the respective holders 4 and 6. The adjustmentnut 21 is operated to adjust the set screw 20 in a vertical direction,i.e. to set a desired welding pressure. Desired electric ratings of thewelding operation are pre-set on the control panel of the weldingcurrent source (not shown).

Then the drive means (not shown) of the reciprocating bar 11 is actuatedto drive the bar 1 1 downwardly in the guides 12, until the bracket 18abuts against the end face of the screw 20.

At that time, the stack of leaf springs 17 (of which one end is rigidlysecured to the upper end of the bar 11) bears at the free end portionupon the head 10 of the bar 7, thus driving the latter downwardly in itsguides 9, until the electrode 29 abuts against the article 33 to bewelded. This article is supported on the bottom electrode 30. As the rod7 is driven downwardly, the spring 9 is compressed, and the leaf springs17 are deformed by a value defined by the spacing between the bracket 18and screw 20 at the beginning of the downward stroke of the bar 11.

The degree of the elastic deformation of the leaf springs 17, which, ashas been already mentioned corresponds to the desired welding pressure,is pre-set by means of the adjustment nut 21, and the pressure can beread on the welding pressure indicator 19.

As the bracket 18 encounters the upper end face of the set screw 20 atthe end of the downward stroke of the bar 11, the stem 22 is drivendownwardly in the bore of the screw 20, and the U-shaped piece 23releases the operating button of the microswitch 24, whereby the weldingcurrent supply source (not shown) is energized for commencing thewelding operation on the article 33. Since the high-current conduit 31in the region adjacent the electrode holder 4 extends normal to thecurrent-carrying housing of the bottom electrode holder 6, any action ofthe electrodynamic forces upon the welding pressure in the zone ofwelding is prevented.

In the modification, where the bottom electrode holder 6 is mounted onthe rod 25 (FIG. 3) which is vertically reciprocable in the guides 26,the welding pressure acting upon the article 33 makes the rod 23 movedownwardly along the guides 26 and deform the leaf springs 28.

In the last-mentioned case, the electrode 30 is able to adjust itselfupwardly and downwardly in operation, to follow up the variations in thevolume of the metal being heated in the welding zone.

By adjusting the degree of the rigidity of the stack of leaf springs 28(e.g. by varying either the cross-sectional area of the springs or theamount of the springs in the stack), it is possible to control theacceleration of drawing together of the electrodes in the zone of theweld, independently of the static welding pressure.

When the welding operation is completed, the footor power-actuated drive(not shown) of the bar 11 is disengaged, and the action of thecompression spring 13 raises the bar 1 1 (FIG. 1) together with the leafsprings 17, the bracket 18 and the welding pressure indicator 19 intotheir respective initial positions. Simultaneously, the compressionspring 34 acts upon the now released stem 22, making the latter moveupwardly in the axial bore of the screw 20, whereby the U-piece 23depresses the button operating the microswitch 24, and the weldingcurrent supply source (not shown) is deenergized. The compression spring9 in the meantime raises the rod 7 into the initial position thereof.

The springs 28 relax (FIG. 3) and raise the rod 25 together with thebottom electrode holder 6 into their initial position.

The herein described welding apparatus is now prepared for commencingthe next welding operation.

It should be noted that the herein disclosed welding apparatus preventssqueezing or splashing of the molten metal beyond the boundaries of theweld.

An apparatus embodying the present invention can be used to greatestadvantage in machines for electric contact microwelding, particularly,in machines for capacitor welding.

What is claimed is:

1. An apparatus for electric contact spot welding, particularly ofsmall-size parts, comprising a housing; a top electrode holder locatedin said housing; a bottom electrode holder disposed in said housingcoaxially with said top electrode holder; ball-type guides in saidhousing; a movable rod mounted in said ball-type guides and supportingsaid top electrode holder; a mechanism adapted to develop a weldingpressure; indicating means registering said pressure; leaf springshaving one end rigidly attached to said mechanism and another end whichfreely bears against the head of said top electrode holder; spring meansby which the top electrode holder is spring-biased against said housing,and electric current conduits adapted to connect said top electrodeholder and said bottom electrode holder to a source of welding current,one of said current conduits, which is adapted to supply said topelectrode holder, extending perpendicular to the housing with theconduit of the bottom electrode holder at a point adjacent to said topelectrode holder.

2. An apparatus as claimed in claim 1, comprising further ball-typeguides, said bottom electrode holder being mounted for verticaldisplacement in said further ball-type guides and having a head freelysupported on one end of the leaf springs, the other end of said leafsprings being rigidly secured to said housing of the apparatus.

1. An apparatus for electric contact spot welding, particularly ofsmall-size parts, comprising a housing; a top electrode holder locatedin said housing; a bottom electrode holder disposed in said housingcoaxially with said top electrode holder; ball-type guides in saidhousing; a movable rod mounted in said ball-type guides and supportingsaid top electrode holder; a mechanism adapted to develop a weldingpressure; indicating means registering said pressure; leaf springshaving one end rigidly attached to said mechanism and another end whichfreely bears against the head of said top electrode holder; spring meansby which the top electrode holder is spring-biased against said housing,and electric current conduits adapted to connect said top electrodeholder and said bottom electrode holder to a source of welding current,one of said current conduits, which is adapted to supply said topelectrode holder, extending perpendicular to the housing with theconduit of the bottom electrode holder at a point adjacent to said topelectrode holder.
 2. An apparatus as claimed in claim 1, comprisingfurther ball-type guides, said bottom electrode holder being mounted forvertical displacement in said further ball-type guides and having a headfreely supported on one end of the leaf springs, the other end of saidleaf springs being rigidly secured to said housing of the apparatus.